This invention relates to modified carbohydrate polymer compositions and cementitious compositions, adhesives and the like containing said modified carbohydrate polymer compositions.
Many adhesives and cementitious compositions such as construction mortars, concretes, and plasters are commonly formulated with a water retention aid to improve the characteristics thereof. For example, ceramic tile adhesives commonly employ a water retention aid in order to prevent absorption of water out of the adhesive mortar into the ceramic tile or substrate to which the tile is to be applied. By employing a water retention aid in the ceramic tile adhesive, the so-called thin-bed ceramic adhesives are possible. Similarly, plasters, crack filling compounds, ceramic extrusions and the like all generally employ a water retention aid in order to prevent the loss of water from the respective mortars and to improve the rheological properties thereof.
Various carbohydrate polymers such as cellulose ethers and starches are commonly employed as water retention aids in the aforementioned applications. Although these carbohydrate polymers work well as water retention aids, they often do not provide the desired rheological properties to the compositions. Recently, it has been found that the rheological properties of the compositions containing carbohydrate polymers are improved with the use of certain additives such as clays, asbestos and long chain organic polymers. While these additives improve the rheological properties of the compositions, their use has several disadvantages. For example, ceramic tile adhesives containing clays and long chain organic polymers often exhibit reduced bonding strength and workability. In addition, such additives are very sensitive to changes in the components of such compositions due to the ionic interaction of these additives with the other components in the composition. In addition, compositions containing such additives are often lumpy and heterogeneous. The use of asbestos, while free from many of these disadvantages, presents a significant health hazard and the use thereof is generally avoided if possible.
Accordingly, a water retention aid for use in cementitious compositions, adhesives and the like, which exhibits good rheological properties and does not significantly impair the other desirable property of compositions containing the water retention aid would be highly desired.